ah, the rollover times are always so fun!
don't get confused during rollover.  age those frags properly.

Reference: /n/atom/patch/applied/49dayfrag
Date: Fri Jun 20 02:54:05 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/ip/ip.h	Fri Jun 20 02:53:50 2014
+++ /sys/src/nix/ip/ip.h	Fri Jun 20 02:53:51 2014
@@ -100,7 +100,7 @@
 	FragOKs,
 	FragFails,
 	FragCreates,
-
+	FragSoftOvf,		/* not a mib */
 	Nipstats,
 };
 
--- /sys/src/nix/ip/ip.c	Fri Jun 20 02:53:55 2014
+++ /sys/src/nix/ip/ip.c	Fri Jun 20 02:53:56 2014
@@ -30,6 +30,7 @@
 [FragOKs]	"FragOKs",
 [FragFails]	"FragFails",
 [FragCreates]	"FragCreates",
+[FragSoftOvf]	"FragSoftOvf",
 };
 
 #define BLKIP(xp)	((Ip4hdr*)((xp)->rp))
@@ -44,6 +45,12 @@
 void		ipfragfree4(IP*, Fragment4*);
 Fragment4*	ipfragallo4(IP*);
 
+static long
+agecmp(ulong a, ulong b)
+{
+	return (long)(a - b);
+}
+
 void
 ip_init_6(Fs *f)
 {
@@ -502,9 +509,9 @@
 		fnext = f->next;	/* because ipfragfree4 changes the list */
 		if(f->src == src && f->dst == dst && f->id == id)
 			break;
-		if(f->age < NOW){
+		if(agecmp(f->age, NOW) < 0){
 			ip->stats[ReasmTimeout]++;
-			/* supposed to icmp ttl exceeded here */
+			/* supposed to: icmpttlexceeded(f, ifc->lifc->local, bp); */
 			ipfragfree4(ip, f);
 		}
 	}
@@ -677,6 +684,7 @@
 		/* free last entry on fraglist */
 		for(f = ip->flisthead4; f->next; f = f->next)
 			;
+		ip->stats[FragSoftOvf]++;
 		ipfragfree4(ip, f);
 	}
 	f = ip->fragfree4;